I'm trying to send a message with strikethrough text in it, and came across this question and its answers, but it doesn't seem to work for Skype for Business.
The keyboard shortcuts page on the Microsoft website only seems to list italics, bold and underline, and the options under "Change font..." only list those three.
Ctrl+B Make the selected text bold.
Ctrl+l Italicize the selected text.
Ctrl+U Underline the selected text.
Currently, the only thing that seems to work is creating strikethrough text in another application (e.g. Microsoft Word) and pasting it into SfB.